Method and apparatus for separating sewing threads and carbon fibers

ABSTRACT

A method and an apparatus for separating sewing threads from pieces of carbon fibre mats or bundles of carbon fibres by means of rollers covered with card clothing. The mat pieces or fibre agglomerates are broken up and separated using the different mechanical properties of the fibres.

PRIORITY CLAIM

This application claims priority to German application serial number 10 2012 025 181.5 filed on Dec. 26, 2012, which is hereby incorporated by reference in its entirety.

The present invention relates to a method and an apparatus for separating sewing threads and carbon fibres.

When carbon fibre mats are processed into formed parts, sewing threads are used to fix the mats. When the formed parts are trimmed, material pieces are generated which are not processed any further, but are recycled. During reprocessing, the sewing threads constitute an obstacle since they act as “predetermined breaking points”. On account of the sewing threads, these recycled fibres can only be used for applications of minor importance and are thus of little value. The sewing threads, i.e. also the connecting threads, do not consist of the same material as the carbon fibres of the mats.

It is obvious to use an optical sorter, e.g. CUBiSCAN, to sort out sewing threads having a different colour than carbon from a fibre and air stream. The drawback of this is that the recycled parts must be torn into small pieces. The threads are not detected and removed entirely.

It is an object of the invention to provide a possibility for gently separating, to the fullest extent possible, the sewing threads from the carbon mats so as to recover the carbon fibres without damaging them and to provide carbon fibres free of sewing threads.

According to the invention, this is accomplished by a method according to Claim 1 and an apparatus according to Claim 10 which do not make use of the colour of the sewing threads (white) as opposed to that of the carbon fibres (black), but rather of the different mechanical properties of sewing threads and carbon fibres, particularly stiffness and surface structure.

The invention will now be explained with reference to FIGS. 1 and 2.

FIG. 1 shows an apparatus according to the invention for separating sewing threads and carbon fibres, comprising a roller 3) covered with card clothing (not shown) around its circumference. Via a taker-in roller 1) and a guiding member 2), carbon fibre mat pieces are fed to the faster turning roller 3). As a result, the mat pieces are broken up. The parts that are still unbroken are held on the roller by means of shaping members A, B, C. Carbon fibres are ejected in unconfined areas or at unconfined edges (e.g., D).

The carbon fibres can be collected in a collection chamber 5) or drawn off by suction. Once the carbon fibres have been ejected, the card clothing is cleared from sewing threads adhering thereto by applying suction. A suction means is shown under 4). Once the sewing threads have been removed by applying suction, new carbon mat pieces can be fed in.

FIG. 2 shows another embodiment comprising several rollers covered with card clothing (which operate in succession). The fibre mat sections and fibres interspersed with sewing threads are fed in through a taker-in device 1) made up of two feed cylinders of the first roller 3) covered with card clothing. The carbon fibres and sewing threads are transferred from one roller to the next and are further broken up as a result of this transfer and by the action of the carding elements 6). Carbon fibres isolated from the fibre mats fall down into the collection area 5) by gravity and are conveyed away. Carbon fibres that have not yet been isolated and those sewing threads which adhere more readily to the card clothing on account of their rougher surface and their greater flexibility are passed to the next roller turning at a higher surface speed. What remains on the last roller is almost exclusively sewing threads which are continuously conveyed away from the roller by a suction device 4) or a doffing device.

Sewing threads and expensive carbon fibres can be gently and highly reliably separated in the manner described above.

While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow. 

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. A method for separating sewing threads and carbon fibres, characterized in that carbon fibre mats, pieces of carbon fibre mats, or carbon fibre agglomerates interspersed with sewing threads are fed to at least one turning roller covered with card clothing and are thus broken up into fibres and fibre bundles and in that the fibres and fibre bundles are carried along by the at least one roller, by means of which at least some of the carbon fibres detach from the at least one roller and at least some of the sewing threads remain on at least one roller.
 2. A method according to claim 1, wherein the fibres and fibre bundles are carried along by the at least one roller until at least 90 percent of the carbon fibres have detached from the at least one roller.
 3. A method according to claim 1, wherein the carbon fibres and sewing threads are carried along by a first roller and are transferred to a further roller which preferably turns at a higher surface speed than the first roller.
 4. A method according to claim 3, wherein the transferring of the carbon fibres and sewing threads from one roller to the next occurs several times, wherein each roller preferably turns at a higher surface speed than the roller before it.
 5. A method according to claim 4, wherein the transferring of the carbon fibres and sewing threads from one roller to the next occurs at least five times with at least six rollers provided one behind the other, wherein each roller preferably turns at a higher surface speed than the roller before it.
 6. A method according to claim 4, wherein the sewing threads are taken off from at least one of the rollers.
 7. A method according to claim 6, wherein the sewing threads are taken off from the last roller in a series of rollers.
 8. A method according to claim 6, wherein the taking off of the sewing threads occurs by suction, a comb or a system of take-off rollers.
 9. A method according to claim 5, wherein the roller is stopped and the sewing threads are then taken off.
 10. A method according to claim 1, wherein the detachment of the carbon fibres from the card clothing of the roller is influenced by at least one of the following: gravity, centrifugal force, air flow, the use of an electrostatic field, and shaping members extending in parallel to a roller axis, across the working width of the roller.
 11. A method according to claim 1, wherein carding rollers or carding members provided opposite to the roller surface process the fibres.
 12. An apparatus for separating sewing threads and carbon fibres, comprising at least one turning roller covered with card clothing for breaking up carbon fibre mats, carbon fibre mat pieces or carbon fibre agglomerates interspersed with sewing threads into fibres and fibre bundles.
 13. An apparatus according to claim 12, comprising several rollers arranged one behind the other such that the carbon fibres and sewing threads are transferred from one roller to the next, wherein each roller preferably turns at a higher surface speed than the roller before it.
 14. An apparatus according to claim 13, comprising at least six rollers arranged one behind the other such that the carbon fibres and sewing threads are transferred from one roller to the next, wherein each roller preferably turns at a higher surface speed than the roller before it.
 15. An apparatus according to claim 12, wherein the card clothing of the at least one roller consists of saw-tooth wire or flexible wires, flexibly mounted wires, or profiles.
 16. An apparatus according to claim 12, further comprising a means for collecting the carbon fibres or drawing them off by suction from the at least one roller.
 17. An apparatus according to claim 12, further comprising a means for taking off the sewing threads from the at least one roller, particularly a suction means, a comb or a system of take-off rollers.
 18. An apparatus according to claim 12, designed so as to comprise a means for influencing the detachment of the carbon fibres from the card clothing of at least one roller by at least one of the following: gravity, centrifugal force, air flow, the use of an electrostatic field, and shaping members (A, B, C) extending in parallel to the roller axis, across the working width of the roller. 